The present invention relates to methods for carrying out measurements of multiphase fluid flow in pipes and ducts, according to the definition in the introduction of the respective subsequent independent claims 1 and 6. There are also disclosed some preferred areas of use of the method according to the invention.
Furthermore, the invention is concerned with measuring the fluid flow rates, the amount of participating particles mixed with fluids, gases etc, or other parameters of the fluids that flow through pipes or ducts in which acoustic sensors are applied, or where safety rules dictate that measuring devices, or parts thereof, can not intrude (completely or partially penetrate through) the pipe or duct.
In connection with production or transport of hydrocarbons (oil, gas and mixtures of these), it may be desirable to measure different parameters of the flow in the pipe. If measurements such as these can be made without making a hole in the pipe wall, i.e. using so called non-intrusive instruments, without special design or modification of standard pipe systems, design and production costs as well as operation costs of the pipe system will be reduced. It will also simplify retrofitting on existing pipes as well as reduce the risk of leakage compared with traditional measuring instruments which require flanges, valves and the like, to get direct access to the flow of fluid in the pipe or the duct.
For example, non-intrusing instruments may be acoustic instruments or temperature probes. For a number years, acoustic, non-intrusing measuring instruments have been known within the oil industry, as well as oil-related industry, to measure amongst other things undesirable fractions of particles such as sand, which may follow the stream of oil and gas.
This type of technology and measuring instruments may also be used in a number of other applications in which fluid, gas and particles, individually, or in an arbitrary combination of these, are being transported through pipes. Illustrative examples are piping systems for transport of coal and water etc, as well as within chemical processing plants. When fluid and particles, individually or in an arbitrary and varying combination of these, are being transported through a pipe, canal or duct, these types of measuring instruments may be applied, as they can be fitted onto one of the outer walls of the duct.
A measuring system which register, with the aid of ultra sound from a passive acoustic sensor, with the aid of its sensing part, the energy that particles in a flow of fluid or gas will emit when they impact the wall of a pipe, is previously known from NO Patent No 301.948. However, it is not possible with a system such as this to determine if the sensor makes satisfactory contact with the pipe wall, and whether this contact changes with time.
Acoustic measuring instruments, operating both in transmitting and receiving modes, and denoted a transducer, operates in a manner so that the transmitter transmits an active pulse which is reflected from the inner surface of the pipe wall, and where the sensor registers the reflected acoustic pulse, are also known. A single transducer (sensor) element, which can alternate between transmission and reception mode, may also be employed. The measuring instruments register the time for the acoustic pulse being transmitted from the transmitter to the reflected pulse being received by the sensor. With knowledge of the speed of sound in the pipe wall, the thickness of the pipe wall can be determined, as well as the possible erosion or corrosion of the pipe wall.
U.S. Pat. No. 5,507,185, discloses ah ultrasonic flow detection system including means for carrying out corrections when the system looses contact (so-called lift-off) with the test object. If such lift-off occurs, a mechanical correction is effected. However, the correction is made by manual operation, i.e. the instrument is moved along the test object by an operator.
Thus, the teaching of the U.S. Pat. No. 5,507,185, is not suitable for applications where the transducer is to be permanent mounted to e.g. an oil/gas conducting pipe on the sea bed, as is the case of the present invention Further,
Further, reference is made to the following patent publications: EP-patent No. 0096.338, GS-patent No. 1.413.755, U.S. Pat. Nos. 5,852,232, 3,906,780, 3,854,323, and 3,816,773.
It is an object of the invention to provide for a new method which may compensate for varying contact between a measuring instrument and a fluid carrying pipe.
It is a further object of the invention to provide for a new method for registering the individual fractions of multi phase fluid flows by using a transducer as disclosed above.
The methods according to this invention are identified by the aspects, which are noted in the characteristics of the thereinafter independent claims 1 and 7 respectively. Preferred embodiments of the methods, according to the present invention, is described in the dependent claims for the methods.
According to the invention, the method(s) are applied according to the aforementioned claims for the methods of registering the fraction of sand in water that is containing sand, as a consequence of erosion, for example in rivers from glaciers and the like. In a river that carries particles as a result of erosion, such as rivers from glaciers, the instrument may be fitted to the underside of a plate, which is placed in the river such that the water containing the particles is flowing over the other surface of the plate, or a representative side stream of the water is brought to flow through a pipe wherein the instrument is fitted to the pipe surface.
According to a preferred application, the software in one or more of the microprocessors which are fitted to in the sensing part of the instrument, may be overwritten, deleted or altered by a new program or new settings/adjustments being transmitted via the sensor signal or power connection.